SCOPE

This
procedure provides instructions for determining the slump flow of self
consolidating concrete in accordance with ASTM C 1611.

SIGNIFICANCE

The
slump flow test is used to determine the filling ability of self consolidating
concrete (SCC). The filling ability gives an indication of the SCC ability to
fill a form under it own weight. SCC mix must be able to fill a form,
passing around reinforcement, without segregation. The Visual Stability
Index gives an indication of the SCC mixes potential for segregation.

PROCEDURE

A.Apparatus

1.Slump
Cone.
The slump cone shall conform to AASHTO T 119: The mold shall be provided with
foot pieces and handles. The mold may be constructed either with or without a
seam. The interior of the mold shall be relatively smooth and free from
projections such as protruding rivets. The mold shall be free of dents.

2.Funnel.

3. Scoop.

4. Tape Measure or Ruler. These should
have at least 1/8 in. (5 mm) gradations.

5.Flow Board. A ¾” (20 mm) plywood board, construction form board
(or other stiff, flat, smooth material) cut 32” X 32” (800mm x 800mm) with
surface sealed to have a non-absorbent face. Draw two centerlines on the board
and two concentric circles, the first circle has a diameter of 20 inches
(500mm). The second circle has a larger diameter, which may be 26 inches (700
mm) in diameter. (Figure 1)

B.Test Procedure

4.Place the
slump cone in the center of the flow board. Cone may be placed either in
the inverted or upright position. Stand on the foot pieces to prevent leakage
when placed in the upright position.

5.Fill the
slump cone in one lift using a funnel. Slightly overfill the concrete above the
top of the mold. No rodding is required since concrete should flow
easily.

6.Trowel
off excess concrete from the top of the slump cone, and remove any concrete
that has fallen onto the board around the cone.

7.Raise
the mold 9 ± 3 in (225 ± 75 mm) in 3 ± 1 seconds by a steady upward lift with
no lateral or torsional motion being imparted to the concrete. Hold in
center position until all concrete has exited the slump cone.

The entire
operation from the start of the filling through removal of the mold shall be
carried out without interruption and shall be completed within an elapsed time
of 2 1/2 minutes.

8.Measure,
to the nearest ¼ inch (5mm), the final flow across the diameter at two points,
900 apart. The two diameter measurements should not be greater than
two inches in difference (if they are it may indicate a sloping board). Report
the slump flow as the average of the two diameter readings.

9.The
concrete should flow out to final slump diameter with no segregation. (Figure
2) Check the edge of the concrete on the board for excessive bleed water called
a mortar halo. (Figure 3) The mix should appear uniform, with the coarse
aggregate visible and evenly dispersed. Report the Visual Stability Index
(VSI) as shown in the table below.

VSI

Criteria

0

No
evidence of segregation in slump flow patty or in the wheelbarrow or
container.

1

No
mortar halo or aggregate pile in the slump flow patty but some slight bleed
or air popping on the surface of the concrete in the wheelbarrow or
container.

2

A
slight mortar halo (<3/8 inch) and/or aggregate pile in the slump flow
patty and highly noticeable bleeding in the wheelbarrow or container.

3

Clearly
segregating by evidence of a large mortar halo (>3/8 inch) and/or large
aggregate pile in the center of the concrete patty and a thick layer of paste
on the surface of the resting concrete in the wheelbarrow or container.

10.Viscosity may be
checked by performing the “Time to T20 test”. To perform this test,
a second person times the flow with a stopwatch. Start timing as the cone
is lifted, stop timing when slump flow reaches the 20 inch (500 mm) mark.

11.For most SCC
applications the concrete should flow out to the T20 (500 mm) mark
in 2 to 7 seconds. If T20 is less than 2 seconds, the mix may be too
thin (low viscosity) and may segregate. If T20 is greater than 7
seconds, the mix may be too thick (high viscosity) and may not flow through the
reinforcing.

Figure
1. Flow Board

Figure
2. Slump Flow Visual Stability Index of 0 – This is a high quality SCC with a
Visual Stability Index of 0. There is no indication of segregation or
separation. Aggregate distribution is good and particles are carried to
the outer edge of the slump flow.